The date is September the 19th 2552. The Halcyon class Cruiser "Filly of Autumn" exits a slip space jump after fleeing the Covenant's destruction of Reach; a Pony colonised planet on Equestria's doorstep that once thrived with Naval activity.
On the other side of slip space, the Filly of Autumn and the thousands of Ponies aboard her discover a mysterious alien ring world, as well as a new batch of Covenant warships.
As the Covenant board the Autumn with the intent of destroying it, Captain Rarity orders the soldiers and personnel to abandon ship, including the ship's AI, Twilight. Only one Pony on board is eligible to keep the AI Twilight safe, but she isn't exactly... "war material." Follow her as she is given the herculean task of protecting Twilight from the might of the Covenant juggernaut and the evil that lies in wait on the ring, with help from her friends and fellow Ponies who will give anything to protect her.